Fix Rails/LinkToBlank auto-correct bug when using symbol for target

[r7kamura]

I fixed a bug on Rails/LinkToBlank auto-correction logic when using a symbol literal for the target value.

Source

link_to 'Click here', 'https://www.example.com', target: :_blank

Expected

link_to 'Click here', 'https://www.example.com', target: :_blank, rel: :noopener

Actual

link_to 'Click here', 'https://www.example.com', target: :_blank, rel: :noopener:

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